Ozone is a strong photochemical oxidant, which may cause serious health
problems and damage to materials and ecosystems. Human exposure to elevated levels of
ozone concentrations can give rise to decreases in lung function and inflammatory
responses. Symptoms observed are cough, chest pain, difficulty in breathing, headache and
eye irritation.

Both laboratory and epidemiological data indicate large variations
between individuals in response to episodic O3 exposure, the effects seem to be
more pronounced in children than in adults [WHO, 1995]. Studies indicate that exposure to
ozone concentrations in the range 160-360 for a period of 1-8 hours reduces various
pulmonary functions.

In view of the harmful effects of photochemical pollution, the Council
adopted in 1992 Directive 92/72/EEC on air pollution by ozone. The Directive defined
threshold values, established procedures for harmonised monitoring, for collecting and
exchanging data and for information of the public when exceedances of threshold values
occur.

More information on the current experience and knowledge concerning
photochemical air pollution may be found in "Tropospheric Ozone in the European
Union, The Consolidated Report" [Beck et al., 1998] which has been prepared
following Article 8 of the Directive.

The thresholds set by the Directive are presented in Table 1. As far as
data reporting is concerned, two types of reporting can be distinguished according to
Article 6 of the Directive:

Exceedances of the population information and warning thresholds (date,
time, duration and maximum concentration) must be reported to the Commission within one
month after occurrence (data is not necessarily validated);

Exceedances of all threshold values including some additional statistics
(percentiles, maxima) must be provided within 6 months after the end of a calendar year
(validated data).

According to Article 7 of the Directive, the Commission prepares a report summarising
all the information transmitted by the Member States at least once a year. The report for
the 1997 calendar year will become available together with this document [De Leeuw and De
Paus, 1998].

In this document a first assessment is made of the 1998 summer season, based only on
the exceedances of the population information and warning thresholds for ozone, which were
transmitted by the Member States after the end of each month.

The report is mainly intended to provide fast feedback to the Member States on their
data. It also enables the Member States to compare the levels observed in the past summer
season with those observed in other Member States. Note that information presented in this
document is not necessarily based on validated monitoring data and hence should be
considered preliminary.

2. Availability of data

According to the Directive, exceedances of the population information
and warning thresholds are to be transmitted to the Commission within one month following
the observation.

This year, for the first time, all 15 EU Member States provided
information on the observed exceedances in time (the deadline for transmitting data was
set at 20 September 1998), or indicated that no exceedances were observed. It is greatly
appreciated by the Commission that MS were able to transmit August exceedance data before
the formal deadline as set in the Directive.

Some countries submitted files which were not formatted according to the
prescribed Commission requirements [Council Directive 92/72/EEC on Air Pollution by Ozone.
Information and data exchange formats. Doc.Rev. 11/243/95]. These files by exception were
converted at the European Topic Centre on Air Quality (ETC-AQ) for further processing.

As was the case in 1997, Ireland, Denmark, Finland and Sweden did not
record any exceedance of the 180 µg/m3 threshold this year.

Table 2 presents an overview of observed exceedances per country per
month.

Member States were requested to check and, if necessary, update the
information on ozone monitoring sites implemented in the framework of the Directive made
available to the Commission. For the interpretation of ozone data it is essential to have
information on the direct surroundings of the station since the ozone concentration may be
scavenged by locally emitted nitrogen oxides or by enhanced dry deposition which might
occur for example under a forest canopy. Member States were requested to classify their
stations as street, urban background1, rural or industrial stations as a first
description of the environment of the stations.

Table 2: Overview of observed exceedances per month per country in
1998. p: exceedance of the population information threshold reported, -: no exceedance
reported, w: exceedance of the threshold for warning of the public reported.

April

May

June

July

August

AT

p

p

p

p

p

BE

-

p

p

-

p

DE

-

p

p

p

P

DK

-

-

-

-

-

ES

p

p

p

p

p

FI

-

-

-

-

-

FR

p

p

p

p

w

GB

p

p

-

p

p

GR

p

p

p

w

p

IE

-

-

-

-

-

IT

p

p

p

p

p

LU

-

p

p

-

p

NL

-

p

p

p

p

PT

-

-

-

-

p

SE

-

-

-

-

-

Only a few countries transmitted information on their operational stations. For other
countries, the 1997 station configuration has been used throughout this report, merged
with the list of stations reporting exceedances during the past summer season.

Map 1 presents the location of all ozone monitoring stations (street and urban
background taken together as 'urban') assumed to be operational during the 1998 summer
season.

1066 ozone monitoring sites are assumed to be operational in the framework of the
Directive. From these, 278 stations are situated in rural areas, 374 stations in urban
background environments, 120 are street stations and 294 stations were characterised as
industrial station or the monitoring environment was not specified. The number of stations
is comparable to the number of stations operational in 1997.

Note that, as only exceedances of thresholds were reported, it is not clear whether
stations were operational continuously. It is possible that ozone concentrations exceeded
a threshold at a site but this was not reported because the monitoring station was
temporarily out of operation.2

In this report exceedances are counted on a daily basis, that is, a day on which a
threshold is exceeded at least once, is calculated as one exceedance day.

Map 1: Ozone monitoring stations implemented in the framework of Directive 92/72/EEC
on air pollution by ozone, scheduled to be operational during 1997.

1 Urban background: station located in the built-up area of
the city but not directly influenced by emission sources such as traffic or industry.

2The annual report [De Leeuw and De Paus, 1998] gives
information on the percentage of time stations were operational, most stations score
>90%.